Separation of sulfuk-containing



June 15, 1954 E; G0R|N 2,681,336

. SEPARATION OF SULFUR-CONTAINING COMPOUNDS BY UREA ADDUCT FORMATION Original Filed Sept. .13, 1949 2 Sheets-Sheet l JNVENTOR. "zfzre Garbo June 15, 1954 2,681,336-

E. GoRlN SEPARATION OF SULFUR-CONTAINING COMPOUNDS BY UREA ADDUCT FORMATION Y Original Filed Sept. 13, 1949 y 2 Sheets-Sheet 2 BY Mg@ Patented June 15, 1954 2,581,336 OFFICE 2,681,336 SEPARATION OF SULFUR-CONTAINING COMPOUNDS BY UREA MATON Everett Gerin, Pittsbur copy-Vacuum Oil ADDUCT FOR- gh, Pa., assigner to So- Company, corporation of New York Incorporated, a

Continuation of application Serial No. 115,516, September 13, 1949. rThis application Novembei' 13, 1951, Serial No. 255,943

The portion of the term to June 16, 1970, h

12 Claims.

vThis invention has to do with the separation of hydrocarbons and hydrocarbon derivatives of different molecular configuration from mixtures containing the same, and also has to do with the preparation of new and novel compositions.

This application is a continuation of application Serial No. 115,516, filed September 13, 1949, which has been abandoned and which, in turn, is a continuation-impart of copending application, Serial No. 4,997, filed January 29, 1948.

I. FIELD OF INVENTION Numerous processes have been developed for the separation of hydrocarbons and hydrocarbon derivatives of different molecular coniiguration by taking advantage of their selective solubility in selected reagents or solvents from which they may later be separated. Exemplary of hydrocarbon separation procedures is the Edeleanu process, wherein parainic materials are separated from aromatics by virtue of the greater solubility of aromatica in liquid sulfur dioxide. Lubricant oil solvent refining processes, solvent deasphalting, solvent dewaxing and the like are further examples of the separation of hydrocarbons of different molecular conguration. Typical of selective solvent procedures for separating hydrocarbon derivatives is the separation of parain wax, monochlorwax and polychlorwaxes, with acetone as the selective solvent.

This invention is concerned with the general eld outlined above, but based upon a diilerent and little-known phenomenon, namely, the differing ability oi hydrocarbons and hydrocarbon derivatives to enter into and to be removed from certain crystalline complexes. As used herein, the term complex broadly denotes a combination of two or more compounds.

This invention is vpredicated upon the knowledge that urea forms complex crystalline compounds to a varying degree with various forms of hydrocarbons and hydrocarbon derivatives.

Il. PRIOR ART For some years it has been known that various isomers of aromatic hydrocarbon derivatives form complexes with urea. Kremann (Monatshefte f, Chemie 28, 1125 (1907) observed that complexes, designated as double compounds,

of urea and the isomeric cresols are stable at difof the patent subsequent as been disclaimed compound was separated from the para isomer and then split up by distillation or with water or acid to obtain pure meta-cresol. The addition compound cf meta-cresci and urea was shown thereafter to have utility as a disinfectant (Priewe, 1,933,757). Bentley and Catlow (1,980,901) found a number of aromatic amines containing at least one basic amino groupv capable of forming double compounds with certain isomeric phenols. It has also been show that trans-oestradiol can be separated from the corresponding cis-compound by forming a dimcultly soluble compound of urea and trans-oestradiol (Priewe, 2,300,134).

vThe forces between urea and the compounds of the foregoing complexes are due to specic chemical interaction between the various functional groups.

One heterocyclic compound, 2:6 lutidine, has been found to form a crystalline compound with urea, thus aiTording a means of separating the lutidine from betaand gamma-picolines (Reithof, 2,295,606).

Comparatively few aliphatic hydrocarbon derivatives have been known to date to form complex compounds with urea. In German patent application B190,197, IV d/ 12 (Technical Oil Mission, Reel 143; Library of Congress, May 22, 1946), Bengen described a method for the separation of aliphatic oxygen-containing compounds (acids, alcohols, aldehydes, esters and ketones) and of straight chain hydrocarbons of at least six carbon atoms from mixtures containing the same, the method being predicated upon the ability of such compounds and hydrocarbons to form Additions-Produkt with urea. In the Technical Oil Mission translation of the Bengen application, however, the urea complexes were designated adducts which term apparently stems from the anglicized addition product.

II'. DEFINITIONS From the foregoing discussion of prior art (II), it will be clear that a variety of terms have been applied to urea complexes. The latter have been ratherl loosely described as double compounds, addition compounds, diiiicultly soluble compounds, Additicns-Produkt, and adducts All of these terms are somewhat ambiguous in that they have also been used to describe products or complexes of diiferent character than the urea complexes under consideration.- This is particularly so Withvthe term adduct, and the related term unadductedv material. While the term adduct is simple and convenient, it is an plexation is also unfortunate designation, inasmuchas it confuses these comple: with other substances known inV applied to Diele-Alder reaction products, formed.

by reaction of conjugated diolens and olefins and their derivatives. As is well' known, Diels- Alder products, as a rule, dol notrevert tov their original constituents when heated or treated with Water, acids, solvents, etc. ,Moreoven the term adduct has been denedearlier as The DIOduct of a reaction between molecules, which occurs in such a way that the original molecules or their residues have their long axes parallel to one another. (Concise Chemical andv Technical Dictionary.) Further ambiguity is introduced by the term adduction, which hasfbeen;` defined as oxidation (Hackh.) v

To avoid the foregoing coniiicting terminology, several related terms have been coined to define with greater specificity the substances involved inthe-phenomenon under consideration. As contemplated herein and as used throughout the specification and appended v claims, Vthe following termsidentiiy the phenomenon Y Plexad-a revertible associated'. complex comprising a plexor, Ysuch as urea, and. at least one other compound; said plexad characterized by reverting. or decomposing, under the influence otheat and/or various solvents, toits original constituents, namely, a plexor and at least one Plexand-a compound capable of forming a 'plexad with a plexor, suchV as urea compounds `of `this character differ in their capacity to "..iorm plexads, dependingA upon various factors described hereinafter.

Y Antiplex--a compound incapable of forming a plexad with a plexor. Plexor-a compound capable of "with'a plexandsuch as urea. PleXate-to form a plexad. Y PleXation-the act, process or eiect of plexating.

i It has now been discovered that certain terminally-substituted straight chain compounds, plexands, form plexads with urea. It has also been discovered urea, a terminally-substituted straightV chain compound can be separated, intheform of a forming a pleXad (d) cyclic Y lcycloalkyl such as cycloprcpyL cyclobutyl,

cyclopentyl, cyclohexyl, cyoloheptyl, chlorcyclohexyl, etc.; aryl such as phenyl and chlorphenyl; hetero such as thienyl C4H3S, furyl Cil-130, Apyrryl Cil-14N, pyridyl C5H4N, thia'zyl' CsHzNS, prazolyl CaHsNz, piperydyl CsHioN, etc.

. (e) kalkenyl As contemplated herein, the invention makes .possible the separation of one or more plexands from a mixture containing the same, such plexz and or plerrandsl being separated in the form of a plexad or'l plexads which, as

, hereinbelow, revert tothe plexor, urea, and the that, by selective vplexation with plexad; from a mixture containing the same and a non-terminally-substituted compound. This separation procedure isz effective also when the paraffin derivatives have the same number of carbon atoms, as in the case' of isomers, or have a different numberV of carbon atoms. Selective effective when they terminal and non-terminal substituents; are different, and-the number of carbon atoms of the substituted paraffins are the same4 or different.

The substituent groups which Imay characterize the Ytern'iinallv-substituted compounds are inorganic and organic groups of the following character:

(a) halogen Y 1E,.Cl, Br and I V(-b) nitrogen-containing NH2, NHR), N32, NO2, NOI-I, CN, CONH2, CONHlR), CONQRM, CNO, CNS, NCO, NCS, etc., wherein R is a hydrocarbon Y radical. (ciA sulfur-containing 1 SH, SR, SOSH, OSOsH, SOzI-, SOzR, Wherein R is a hydrocarbon radical, S022. where- 'inZ' isa halogen atom, etc.

plexand or plexands under certain conditions. The separation, therefore, isan excellent means fonobtaining, in pure or concentrated form,'one onmore plexands or antiplexes Vwhichever is' the desired material." The invention also providesa means olforming new compositions of matter, namely, a number or plexads which .may beused as` a source'of a plexor, urea, or as a source of a plexand.

V. OBJECTS itY is an object of vthis invention, therefore, to provide an 'effective `rneansdor separating hydrocarbons and hydrocarbon derivatives of different molecular coniiguration from' mixtures containing thesame.

It is also an object' of this invention tofselectively. separate terminally-substituted straight chain compounds from mixturesv containing the same. Y

A furtherv object is toseparate a terminallysubstituted straight chain compound from'amixture containing the same and a non-terminally substituted isomer.

,Still another object is to separate a terminallysubstituted straight chain compound from a mixture containing the same and a non-terminallysubstituted straight chain compound having a Y diiierent number 'of carbon atoms. Y

An additional object is to separate a terminally- Vsubstituted straight chain compound from a non-terminally substituted compound,` ywherein thesubstituents are different and the number. of

carbon atoms of the respective compounds vare the same.A A related object is to separate a terminally-substituted straight chain compound from a non-terminally-substituted compound, wherein thesubstituents are diierent and the number of carbon atoms of ,theY respective compounds are different. Y

, A further object is to separate a non-terminally substituted compound from a` mixture Containing the same. and, a second VVnon-terminally-substituted compound less susceptible to plexation. Y

Another important object is, the provision of a continuous. method of separation of said plexands and antiplexes, which method is flexible, capable Vof relatively sharp separation, and not highly de- 4` manding of attention and of utilities such as heat, refrigeration, pumping power, and the like. An additional object is to provideV a pleXand or plexands ysubstantially free of an'antiplex orv antipiexes. A'corresponding object is the provision of anantiplexor antiplexes substantiallyv free of said plexand or plexands. l Y f Y Another object is to provide anew` `and-novel class o1' sub-classesof plexads comprising a" plexdescribed in detail Y and and urea. A related object is the provision of a new and novel class or sub-classes of plexads comprising a secondary plexand and urea.

l Other objects and advantages of the invention will be apparent from the following description.

VI. vINVEN'ZIION IN DETAIL As indicated above, it has been found that the foregoing objects are achieved by plexation with urea (a plexor) of a pleXand or plexands.

(1) PLExANDs Plexands contemplated herein are represented by the general formula (A) (A) X(CH2)CH3 wherein n is a whole number and wherein X is a substituent group of the character described above, with n and X being interrelated.

The substituent group X may be any of the types outlined above, subject, however, to one important restriction, namely, that of geometrical size. Two dimensions are of importance in determining the nature of the separation that may be obtained between compounds-plexands and antipleXes-given above. The rst dimension is the cross-section of the group (X) taken in a direction perpendicular to the bond joining the group (X) to the parent hydrocarbon. This distancewidth-is taken at the widest portion of the group and may be conveniently given a quantitative measure as the distance from between outer covalent radii of the two most widely separated atoms along the cross-section of the group where the covalent radii are those given by Pauling (Pauling, "Nature of the Chemical Bond; Corf nell University Press; Ithaca, N. Y.; 1939). The second distance-length-is the projection -along the bond joining the group to the parent hydrocarbon of the distance from the center of the carbon atom to which the group is attached, ,1.

to the center of the atom whose covalent radius shell extends furthest in the direction of said bond, plus the covalent radius of said bond.

The rst distance determines the length of the aliphatic chain required to obtain plexation at room temperature (25 C.) with a saturated urea solution, a plexor, when the group (X) in question is attached to the terminal carbon atom of the aliphatic chain. In the case of composite groups of the type -eCOY, -CHsCOY and CI-IzY, where Y is a non-aliphatic radical such as chlorine or amino, the =CO, -CHzCO and -CHzconstituents, respectively, are considered as part of the aliphatic chain and the width computed is that for the radical Y.

The widths of a number of typical groups computed according to the method given above vare listed in order of size in Table I below:

TABLE L WIDTH 0E VARIOUS GROUPS 1N A or M-tolyl 6.09v

The correlation between the width of the group and the length of the aliphatic chain required for plexad formation at room temperature is an approximate one. This relationship 5 depends to some extent upon the nature of the group (X) as well as upon the width of the group (X). For example, in the case where two groups (X) are the same size, the group which imparts a higher melting point to the substituted paraiin will form the stronger pleXad, i. e., will form a plexad when the aliphatic chain is somewhat shorter in length.

Only the carbon atoms in the chain are considered to contribute to the chain length, that is, l5 atoms such as oxygen, sulfur, nitrogen, etc., are not included in the atom total. Accordingly, then, the straight chain compounds contemplated herein include straight chain aliphatic hydrocarbons and straight chain aliphatic hydrocar J bons in which one or more of the carbon atoms of the chain have been replaced by such atoms as oxygen, sulfur, nitrogen, and the like.

It is possible, however, to give the unequivocal limits for the relation between width of the group (X) and size of the carbon chain required for plexation with urea at room temperature, 25 C. These limits are set forth in Table II below:

TABLE nfooRRELATIoN BETWEEN GROUP (X) AND MINIMUM CHAIN UREA PLEXATION AT 25C.

WIDTH OF 3() LENGTH FOR Minimum Chain Length, Number of Carbon Atoms It is to be understood that these limits apply for plexation at temperatures of the order of about 25 C. The minimum number of carbon 4J atoms in the chain is generally -lower for pleXation at lower temperatures, but generally not more than one or two carbon atoms lower. n the saine vein, for an increase in temperature, a correspondingly higher number of carbon atoms will be required in the carbon chain.

By way of illustration, the following compounds are typical plexands: (a) halogen compounds:

n-heptyl uoride, n-heptyl bromide, n-octyl chloride, n-octy1 bromide, n-hexadecyl chloride, n-hexadecyl bromide, n-octaV decyl chloride, n-octadecyl bromide, etc. (b) nitrogen-containing compounds:

aminon-octylamine, n-decyl amine, n-hexadecyl amine, n-octadecyl amine, noctadecenyl amine, methyl, n-octyl amine; butyl, n-octyl amine; etc. cyanon-hexyl nitrile, n-octyl nitrile, n-tetradecyl nitrile, n-octadecyl nitrile, etc. nitro- 1nitrondecene, 1-nitro-n-dodecane,

l-nitro-n-octadecane, etc. amidon-octanamide; n-dodecanamide; n-oc- 'tadecanamidm n-octadecenamide; N- methyl, n-octanamide; N-hexyl, nl decanamide; etc.

7 cyanate and socyanate" n-heXyl cyanate, n-hexyl isocyanate, ndecyl cyanate, n-decyl isocyanate, nhexadeoyl cyanate, n-hexadecyl isocyanate, etc.

thioeyanate and isothiocyanate- Y n-decyl thiocyanate, n-decyl isothiocyanate, n-octadecyl thioeyanate, noctadecyl isothioeyanate, etc. sulfur-containing` compounds: mercapton-octyl mercaptan, n-dodecyl mercaptan, n-hexadeoyl meroaptan, n-octadecenyl mercaptan, etc. Suldo (SR).-

methyl, n-octyl sulfide; butyl, n-dodecyl sulfide; amyl, n-hexadeeyl sulfide;

etc. Y sulfaton-dodeeyl sulfate;

, ete. sulronyl halide-- Y n-decyl sulionyl chloride, n-dodeoyl sul- `fonyl bromide, n-hexadecyl sulfonyl iodide, etc. cyclicY substituent: 1cyclopropyl-n-octadecane, l-cyclohexylri-liexadetane,Y lr-phenyl-n-oetadecane, 1- thienyl-n-octadecane, etc.

It is to be understood that ternfiinally-substi-V tuted straight chain compounds .containing a second terminal substituent on the opposite terminal carbon atom, are also contemplated herein as plexands. Such disubstituted compounds are also subject to approximately the foregoing relationships of terminal group width and chain length.' Compounds oiY this character are represented'by the following general formula:

n-hexadecyl sulfate,

wherein u is a whole number, and X and X are the same or diierent and as deiined above.

Illustrative of suchY compounds are:

1,10-dichlor-n-decane;

1,8-netane diamine; 1,10-11-decane dia-mide; 1,12-n-dodecane dithiol; L-disulfo-n-oetadecane; ete. Y

Another class of compounds contemplated herein as plexands are those having a non-terminal substituent, and being represented by gen-V Vnature of,V thegroup. Thus, in compounds of this type,r the minimum chain length required for plexation is determined by the length of group H3C(CII2)7-., if 1' is Vsmall enough so that this alkylv group is shorter in stituent group (X). t is possible, bearing this relationship in mind, however', also to give rather f length than the sub- Lil) "wide limits in thecorrelation of group length with the minimum chain Ylength required for in Table IV, also provided below:

TABLE n1 "NHZ .'f

SH 2.85, -Br 3.05

-CHzCl 3,11

v--C'N 3.25

-SOaI-I 3.37

-Cyclohexyl (average configuration), ,5.09

-Phenyl 5.69

Minimum Chain Length, Number of Carbonk Atoms Group It is to be understood, once again, that the llimits shown in Table IV apply for plexationv at temperatures of about 25 C. Here too, the mini'' mum number of carbon atoms in the chainfis somewhat lower for plexation at lower tempera-I tures, but generally not more than one or-'two carbon atoms flower. higher number of carbon atoms will be required in the chain for a rise in temperature.

Representative of the foregoing plexandsare the following:

2-ehloro-n'tetracosane; Z-bromo-n-tetracosane; 2-amino-n-decane; 2-nitro-neoctadecane; etc.

Considering the relationships shown by .Tables III and IV, it will be seen that 2-chloro-noctadecane, for example, will form a plexad with A`urea at about 25 C. `This, then, illustrates a pleXad comprising a secondary plexand and urea. Y

general formuia (A) above, separated fromra compound represented by general formula (B) above, wherein the halogen atoms and the V.nurnber of carbonatomsthereof are the same.

A further illustration stemming from the 'foref going data is the ei'icient separation of V1chloro n-octadecane from a Vmixture oi the same and same and 2-chlorio-nfcosane thusV demonstrating .the .separation of a compound yrepresented REQUIRED FOR UREA Also, a correspondingly' Y9 by general formula (A) above, from a compound represented by general formula (C) wherein the sum of r-I-m is other than n-Z, and wherein the halogen atom is the same as in (A).

As mentioned earlier, two paramn derivatives of the same chain length but having different substituents can be separated by plexation. This feature is illustrated by selective plexad formation of -chloro-n-octane in a mixture containing the latter and 2-bron1o-n-octane. This may be referred to as the separation of a monohalide represented by general formula (A) from a monohalide represented by general formula (D):

(D) HaCwHcfoHHamoH 2li, wherein the sum of r-i-m is equal to n-2, and wherein the halogen atom X is different from X in (A).

Still another separation which is eifected readily is that of l-chloro-n-octane from a mixture containing the same and 2-bromo-n-heptane or a mixture of the same and 2-bromo-n-nonane, that is, wherein the number of carbon atoms and the halogen atoms are dierent. This is the separation of a compound represented by general formula (A) from a compound represented by general formula (E):

(E) HaC(CH2)rCH(CH2)mCHs wherein the sum of r-l-m is other than n-Z and wherein the halogen atom X is diierent from X in (A).

Among the various sulfur-containing compounds shown above are straight-chain suldes represented by general formula (F):

(F) Ri-S-Rz wherein R1 and R2 are n-alkyl groups or terminally-substituted n-alkyl groups, and wherein the total number of carbon atoms of R1 and R2 is at least about eight.

Sulfides of the type represented by (F) form strong plexads with urea, in contrast with sulfides in which R1 and R2 are branched-chain alkyl groups or are other than terminally-substituted, straight-chain alkyl groups; the latter (2) ANTIPLEX An antiplex, as defined above, is a compound incapable of forming a plexad with a plexor, such as urea.

(3) PLExoR The plexor used herein is urea, which is in solution in a singleor multiple-component solvent. This solution should range from partially saturated to supersaturated at the temperature at which it is contacted with a plexand or with a mixture containing one or more plexands and antiplexes, and, in many cases, it will be found convenient to suspend a further supply of urea crystals in the solution, handling it as a slurry. For gravity or centrifugal separation, it is convenient to use a solvent of such a specific gravity that after the formation of a desired amount of plexad, the speciiic gravity of the solvent phase will be different from that of the plexad phase and of the antiplex phase to a degree sufficient to permit separation by gravity, centrifuging, etc.

The solvent should be substantially inert to the plexand and to the compounds of the mixture and also to the urea. Preferably, it should also be heat stable, both alone and in contact with urea, at temperatures at which the desired plexad is not heat stable.

As indicated above, the solvent may be either singleor multiple-component. It is sometimes convenient, particularly where the plexad is separated by gravity, to utilize a two-component system, as water and an alcohol, glycol, amine or diamine, and preferably a lower aliphatic alcohcl such as methanol or ethanol, or a Watersoluble amine such as piperidine. Such a solvent, partially saturated to supersaturated with urea, lends itself readily to a continuous process for separation by plexation.

Solutions containing suicient water in order to minimize the solubility of the hydrocarbon derivatives in the urea solvent are often employed. The minimum quantity of water required in such instances depends upon the polarity and the molecular weight of the hydrocarbon derivative, or plexand, being treated and, in general, this quantity will be greater with more polar plexands and with lower molecular weight compounds.

In certain cases the use of single-component solvents is advantageous. Single-component solvents other than alcohols may be employed, although they are normally not as useful as the lower aliphatic alcohols. Glycols may be employed as single solvents, yet ethylene glycol is generally not suitable in gravity separation operations due to the high density of the urea-saturated solvent. The higher glycols and particularly the butylene glycols may be advantageously employed. Diamines such as diaminoethane, propane and -butane may likewise be employed. Additional useful solvents include formic acid, acetic acid, formamide and acetonitrile, although the first three of these are subject to the same limitation as ethylene glycol.

Solvents generally useful When mixed with sufficient water, ethylene glycol or ethylene diamine, to render them substantially insoluble in the derivatives being treated, a're selected from the class of alcohols such as methanol, ethanol, propanol, etc.; ethers such as ethylene glycol diethyl ether; and amines such as triethylamine, hexylamine, piperidine. When gravity separation is employed, the mixed solvent is preferably subject to the restriction that the density after saturation with urea must be less than 1.0-1.1.

(4) TYPICAL SEPARATIONS In order that this invention may be more readily understood, typical separations are described below with reference being made to the drawings attached hereto.

(a) Separation of plezvcmd from omtzplec:

The procedure which may be employed in effecting the separation of terminally-substituted and joins the charge from from non-terminally-substituted, straight chainy plexad obtained inthe treatment of terminally substituted and non-terminally-substituted chlo rides or bromides of normal -parains containing from 8-l6 carbon atoms. i

In Figure l, a charge comprising `a plexand and an antiplex, for example l-bromo-n-octane and z-bromo-n-octane, respectively, enters through line I, to be contacted with urea solution from line 2, and the charge and solution are intimately mixed in mixer. In case the charge undergoing treatment israther viscous at the urea solution, thus. reconstituted to its original condition by'return to it of that portion of the urea which passed into plexad, is withdrawn from settler I6 by line 2 and returned to process. Naturally, in a process oi this kind there are minor mechanical and entrainment losses of Y urea solution, etc., and urea solution makeup is temperature of plexad (1bromo-n-octaneurea) Y formation, it is advisable to provide a diluent, such as for example, a naphtha cut which may be recycled within the process, as described later,

up is provided by line li.

From mixer 3, wherein there is achieved an intimate mixture of urea solution and charge, the mixture flows through line 6, heat exchanger "i, and cooler 8 into settler 9. There may be some or a good portion of plexad (l-bromo-n-octane'- urea) formed in mixer 3, but in general, it is Vpreferred to operate mixer 3, at a, temperature somewhat above that conductive to heavy formation of plexad. Then, in heat exchanger 1, the temperature of the lmixture is reduced, and in cooler 8 adjusted, so that the desired plexad is formed. It will be recognized that this showing is diagrammatic, and Vthat the heat exchangers and coolers, heaters, etc., shown will be of any type suitable, as determined by the physical characteristics of the materials being handled.

From cooler ii, the plex'ad-containingrmixture ows into settler 9. This settler Vis preferable so managed that there is an upper phase oi antiplex (Z-brOmO-mOctane), an intermediate phase of urea solution, and a lower region containing a slurry 'of plexad in the urea` solution. The incoming mixture is p-referably'introduced into thev solution phase, so that the antiplex (2-brorno-noctane) may move upward and piexad downward, through some little distance in the solution, to permit adequate separation of plexad from antiplex and antiplex from plexad.

Antiplex will be removed from settler 9 by line i0 and introduced into fractionator il, wherein the diluent is removed, to pass overhead by vapor line l2 and eventually to usethrough line il. Recovered antiplex (Z-brOmo-n-octane) from the system through line I3. Obviously if no diluent be used, fractionator il will'be dispensed with'.

Plexad and urea solution, withdrawn from settler v9 through line IB, are passed through heat exchanger 1 and heater i5 to enter settler i6 through line Il. In this operation, the temperature is so adjusted that the Vplexand (l-bromon-octane) is freed from the plexad and, in settler IS, theplexand rises to the top to be recovered from the system by meansV of line I8. The

line 4. Diluent makeV -p asses,

' Y tion and plexad pass through iine iii.

provided for byline i9.

In many cases, the separation or' plexad and solution from antiplex may be conducted with greater facilityV in a centrifuge operation. Such a setup is shown in Figure 2, wherein only the' equivalent of that portion of Figure l `centering reproduced. Again in diagram form, the cooled mixtureV containing antipl'ex, plexad and urea solution enters centrifuge 20 through line '5. In many cases, it will be desirable to utilize a Vcarrier liquid in known manner in this operation and that liquid may .be introduced by line 2l. fintiplex will be carried ofi through line it, and plexad, urea solution, and carrier, if present, pass through line 22 to a about settler ii is separation step, which may include washing and' maybe carried out in a settler, a filter, or another centrifugal operation, which separation is indicated diagramrnatically at 23.V Carrier liquid, ii used, returns through line 2d, and urea solu- (No-te: lines e, it and ifiare the same lines, for the same functions, as in Figure 1A and, are identically numbered) i (b) Separation of one plexand from arsecond pierced In the case where both the terminally-substituted and non-terminally-substituted com-l pounds form plexads, a concentration of' the ter- Y minallwsubstituted compound will be obtained. The sharpnessof separation of the terminallysubstituted compound will the difference in the strength of the plexads formed with the two types of pure compounds. In general, this will be greater, the shorter the carbon chain length'of parent hydrocarbon. For

example,` substantially pure l-bromonoctane can'be obtained from amixture with Z-bromon-octane in a single plexation. It is more diicult, however, to obtain separation between 1- chloro-n-octadecane and 2-chloro-n-octadecane.

Thefollcwing serves to illustrate a procedure for obtaining sharp separation between one plexand, l-chloro-n-octadeoane, and a second plexand, Z-chloro-n-octadecane, the latter behaving as a secondary plexand in formi-ng a Vplexad. rIhis procedure is similar to a sweat-- procedure used in the ing or a solvent sweating refining of slack waxes, and is shown diagrammaticallyV in Figure 3.

in Figure 3, a slurry of solid urea in a saturated urea solvent, which is preferable an aqueous alcoholic solution, is pumped from Vline 3l into a turbo mixer 32 where it is agitated with a mixsolvent; or (3) greater density than the urea solvent. The ainountof excess solid urea are employed' should be suiicient so that afterv the plex-'f t ation is completed the urea solvent remains Vsubstantially saturated with urea.

Internal cooling means may be .employed in be greater, the greater n relatively high vis` cosity; (2) an appreciable solubility in the ureaY 13 32 to further cool the mixture and remove the heat evolved during the plexation. The temperature employed in 32 will depend upon the chain length of the plexand and secondary plexand. If the chain length is such that it is not more than one or two carbon atoms greater than the minimum required to obtain plexation with the pure plexand at 25 C., then temperatures in the range of to 20 C. should be employed. If the chain length is from two to six carbon atoms greater than the minimum, temperature in the range of 15-30 C. should be employed; and if the chain length is greater than six carbon atoms beyond the minimum, temperatures from 25- 50 C. may be employed. It will be apparent,then, that conditions of operation vary considerably, conditions selected being those appropriate for the formation of the desired plexad or plexads.

The slurry of plexad, urea solvent and secondary plexand is pumped, by means of pump 36, through line 35 and cooler 31 wherein it may be further cooled if desired, and into gravity settler 38. In settler 38 the secondary plexand plus naphtha solvent rises to the top and is withdrawn through line 39 into fractionator 40. The secondary plexand, predominantly Z-chloro-noctadecane, is removed as bottoms from fractionator through line M. The naphtha solvent is taken from fractionator 40 through line 52, cooler 53, tank 45 and line 45 to be employed in solvent sweating zone 4B. Naphtha solvent may also be recycled to fractionator 40 through line 41, by means of pump 48.

In settler 38, the slurry of plexad in urea solvent is taken ofi through line 49, heat exchanger 50 and heater 5I into solvent sweating zone (or mixer) 6. A portion of the clear urea solvent may be removed from the center of 38 and recycled, through line 5l and pump 52, to mixer 32 if desired.

CHAIN LENGTH plexad is thus heated hot enough to cause com plete decomposition of reversion of the plexads.

and solution of the urea in the urea solvent. Temperatures in the range of 55-85" C. are generally suitable.

Plexand, 1 chloro n octadecane, contaminated with naphtha which had been occluded on the corresponding plexad (l-chloro-n-octade cane-urea) is withdrawn through line 55 into fractionator 6l. Naphtha is taken off overhead from fractionator 5i through line 52, cooler 63, tank 56, pump 55 and line 55, to mixer 3l. A portion of the naphtha may also be recycled to fractionator 5l through line 5l'. Plexand is recovered as bottoms through line 38.

Urea solution is recycled from the bottom of settler 59 through line 59, pump 1G, heat exchangers 57 and 50, and line 5|.

Plexand of any desired purity may be obtained by either: (l) increasing the fraction of the total plexad decomposed in the solvent sweating zone (5), or (2) including a multiplicity of alternating solvent sweating zones (5) and settling Zones (55) operated in series.

VTI. ILLUSTRATVE EXAMPLES The following examples serve to illustrate, and not in any sense limit the present invention.

(a) TerminaZZy-substituted straight chain para]- fins general formula A:

A number of such paraiiin derivatives of varying chain length were agitated for several hours with water or with aqueous methanol solutions saturated with urea, and plexad formation was evidenced by resulting precipitate. The results are summarized in Table V, below, and the minimum chain length required for plexation found experimentally is compared with the correlations given in Table IV. Table V is as follows:

LENGTHS REQUIRED FOR UREA R HYDROCARBONS-l DETERMINED EXPERIMEN- IN TABLE IL-PLEXAD FORMATION-ALIPHATIC G ChMinifllum roup ain ength Group 4 5 6 7 8 10 12 16 18 N o. Correlation,

Table I I -CONH2-..- 1 5-8 Cl l 5 8 -Br 1 5-8 CIL 1 5-8 -NH2 1 5-8 -Thienyl 3 12-18 It is to be understood that the gravity settler 38 may be replaced by other separation means such as a centrifuge or rotary lter, etc.

'I'he mixture of solvent and plexad is heated in solvent sweating zone 46 to a temperature suicient to decompose the major portion of the plexad of the 2-chloro-n-octadecane, while preserving the major portion of the plexad of 1- chloro-n-octadecane. The temperature employed in Zone 135 is related to that employed in mixer 32, and will generally be maintained from 10-20" C. higher in zone 46 than in mixer 32.

The partially decomposed plexads, urea solvent, and naphtha mixture is passed from Zone through line 53 to settler 54. The naphtha containing plexand, 1-chloro-n-octadecane, and some secondary plexand, 2-chloro-n-octadecane, is recycled through lines 55 and 33 to mixer 32. The slurry of undecomposed plexad is withdrawn from the bottom of settler 54 through line 55, heat exchanger 51, heater 58 into settler 59. The

It will be noted from the data set forth in Table V that, in all instances, experimental values found for the minimum chain length are witmn the limits specified in Table II.

(b) Comparison of equilibrium values in, the plea:- atz'on of compounds of general formula (A) and (B) pairs of compounds, (A)

urea and tuted'hydrocarbonis iso-octane with a 70% methanol-30% water solution saturated with noting the minimum concentration required for plexad formation. The results are summarized in Table VII, below.

TABLE VIL-EQUILIBRIUM VALUES IN TBE UREA IIIBISATION OF HYDROCARBON-l, HYDROCARBON-2 Equilibrium i From the data shown in Table VII, it will be noted that the. terminally-substituted compound (A), forms ya plexed, while the non-terminallysubstituted compounds (B) do not form plexads. When the compound (B) does not form a plexad, relativelylsharp separation rcan be obtained between compounds (A) andr(B) in a single plexation. Y

(c) Separation of lbromo-nY-'octane and 2- The following solution was contacted with urea, in a reaction vessel: equal parts by volume of 1- bromo-n-octane, Z-brorno-n-octane and 2-methyl pentane. A portion, 45 parts by volume, of this solution was agitated at room temperature (25 C.) with 5() parts byv volume of) an aqueous 80% methanol solution saturated with urea at 45 C. A plexad was formedv and settled to the bottom of the urea solution. rif'he upperlayeniree of plexe ad, was decanted from the lower layer, rlhe upper Y whereupon Z-methyl pentaneV equilibrium value, namely, 18.7 volume per cent..

Vin. yirrrmfrr From the foregoing description, it will be apparent thatthe invention has considerable application in the chemical and related arts. Forexample, terminally sulfonated parains Y may be separated from the nonfterminally substituted compounds in the manufacture of detergents and 'wetting agents by the sulfochlorination of parri'his makes possible purer and' more eiiif ains. Y Y cient detergents and wetting agents. Similarly, l'chlorostraight chain parafiinsmay be separated from the corresponding non-terminally substituted chloro compounds, which are formed in thechiorinatio-nof straight chain parafns.

Also, in the high temperature, vapor-phase chlorinationof olefms, two. principal products'are produced, namely, the 1-ch1oro2-o1en andthe pentane and then deco-m'-V f 16 S-chloro-l-olenn according to the following representation: Y v

RCH2QH=GH2+ C12 v RcH-oihonz RcH=CHcHo1 HC1 c1 v Y The present method may be employed tofeifect Y the separation between the foregoing l-chloro Y'll-olefins', for example, byrresort and the 3-chloro compounds.

The addition of a'rnercaptan or hydrogen bro'- rnide to a l-olen in the presence of air, oxygen or peroxides takes place with the addition oi the mercapto radical, -SR, or bromo radical, Br, to the terminal carbon atom of the oleiin. If an olefin mixture containing a straight chain l-olen'is so treated, the derivatives obtained from the straight chain l-olen can be selectively separated by urea plexation. The l-olen derivatives obtained in this manner may be used for various purposes, or can known reactions to other useful products. YFor examplathe bromide may be pyrolyzed to regenerate the pure l-olen.

The inventionis also applicable tothe separation of a straight-chain suliide from a branched chain sulfide fo-rmedby reaction of a mercaptan or hydrogen suliide with an oleiin mixtiue containing a boletin, reaction generallybeing ef"- ffected inV the ,presence of oxygen or peroxide.V

The Vl-oleiin may be Vregenerated from thel straight-chain suide by decomposing the latter, for example, contact in the vapor phase at atmospheric pressure with suitable catalysts at 30G-400 C., or by direct thermal pyrolysis. Accordingly, the-invention is suitable for separating pure l-olefins from thermally-cracked waxy materials, Fischer-Tropsch products, andv the like. In addition, straight-chain suliidedV and terminal mercaptans can be separated from high sulfur content kerosene and gas oils; sulfur com-` pounds sofseparated may be used asa source of to vapor `phase decomposition.`

Not only Vare the separation procedures contemplated herein useful for removing substantial amounts of a contaminating constituents,V

as an isomer or isomers, from a'related compound, but theypare of Value'when small or trace amounts of such an undesirable constituent are present. f

Y In addition, thenew plexads madeY available herein constitute desirable sources of urea and of the vario-us plexands associated therewith. For example, the desired compounds can be kept Vin storage or shipped until just prior to use,

when they are separated by reversion of the Y plexads. f

Halogen compounds can be plexated from mix-V Y tures containing the same and form urea plexads,

as described, above andas described and claimed Y in application Serial No. 115,511, which application has been abandoned in favor of applaiiirr Y Serial NO. 374, "7, ile-d August 17', 1953. COmpounds characterized by a nitrogenucontaining substituent are also plexated from mixtures con-x taining thesame and form plexads with urea, as described above'this subject matter is also described and claimedl in application Serial No. 115,515. Application Serial No. liG'LlQ'Z'ylJas filed February 1,1954, as a division of the last-mem tioned application. Plexation of compounds con-v taining..y cyclic substituents, and urea; plexads thereof, are described and' are claimedv in application Serial. No. 116,593. Plexation withv ureay of various terminally'lsubstituted compounds be converted by 17 from mixtures containing the same and nonterminally substituted compounds, described above, is also described and claimed in application Serial No. 115,517.

Urea plexation of a non-terminally monosubstituted compound from mixtures containing the same and a non-terminally poly-substituted compound is described and is claimed in application Serial No. 115,513, now U. S. Letters Patent No. 2,642,422. Urea plexation of mixtures containing aliphatid compounds of different degrees of unsaturation is described and is claimed in application Serial No. 115,514; similarly, plexation of mixtures containing aliphatic hydrocarbons of diierent degrees of unsaturation and urea plexads of such hydrocarbons, are described and are claimed in application Serial No. 115,518, now U. S. Letters Patent No. 2,642,423, and in divisional application thereof Serial No. 266,547, filed January 15, 1952. Application Serial No. 410,573, filed February 16, 1954, is a division of application Serial No. 266,547, led January 15, 1952, which, in turn, is ardivision of said application Serial No. 115,518 (now Patent No. 2,642,423).

Said applications Serial Nos. 115,511; 115,513 through 115,515; 115,517; 115,518 and 116,593 were led concurrently with said parent application 115,516 on September 13, 1949.

I claim:

1. The method of separating a straight chain aliphatic compound (I) containing a sulfur-containing terminal substituent and having in the chain at least about: 12 to 18 carbon atoms when the "width of said substituent is between about 3.7A and about 5.2A and 18 carbon atoms when the width of said substituent is greater than about 5.2A, from a mixture containing the same and at least one sulfur-containing compound (II) less susceptible to urea complex formation than said sulfur-containing compound (I), which comprises: contacting said mixture with urea under conditions appropriate for the formation of a crystalline complex of urea and said sulfur-containing compound (I) and separating said complex from the resulting reaction mixture.

2. The method of separating a saturated straight chain aliphatic compound (I) containing a sulfur-containing substituent and having in the chain at least about: 12 to 18 carbon atoms when the width of said substituent is between about 3.7A and about 5.2A and 18 carbon atoms when the Width of said substituent is greater than about 5.2A, from a mixture containing the same and at least one sulfur-containing compound (II) less susceptible to urea complex formation than said sulfur-containing compound (I), which comprises: contacting said mixture with urea under conditions appropriate for the formation of a crystalline complex of urea and said sulfur-containing compound (I) and separating said complex from the resulting reaction mixture.

3. The method of claim 2 wherein said sulfurcontaining compound (I) is a monosulfate having at least about 12 carbon atoms in the chain.

4. The method of separating a straight chain aliphatic compound represented by general formula (A):

when the width of X is between about 3.7A and about 5.2A, and 16 when the widt of X 18 is greater than about 5.2A". from a mixture containing the same and an isomer thereof represented by general formula (B) (B) mOHnroHHvmcH wherein X is an identical sulfur-containing group, and r and m are integers the sum of which is equal to n-2, which comprises: contacting said mixture with urea under conditions appropriate for the formation of a crytalline complex of urea and said compound (A) and separating said complex from the resulting reaction mixture.

5. The method of separating a straight chain. aliphatic derivative represented by general formula (A) (A) X(CH2)1LCm wherein X is a sulfur-containing group, and n is a whole number greater than about: 10 to 16 when the width of X is between about 3.7A and about 5.2A, and 16 when the Width of X is greater than about 5.2A", from a mixture containing the same and an aliphatic compound represented by general formula (C) (A) X(CH2) nCHs wherein X is a sulfur-containing group, and n is a whole number greater than about: 10 to 16 when the width of X is between about 3.7A and about 5.2A, and 16 when the width of X is greater than about 5.2A, from a mixture containing the same and an aliphatic compound represented by general formula (D):

' when the width Xl wherein X is a different sulfur-containing group than X, and r and m are integers the sum of which is equal to n-2, which comprises: contacting said mixture with urea under conditions appropriate for the formation of a crystalline complex of urea and said compound (A); and separating said complex, from the resulting reaction mixture.

7. I'he method of separating a straight chain aliphatic derivative represented by general formula (A):

(A) X(CH2) CH3 wherein X is a sulfur-containing group, and n is a whole number greater than about: 10 to 16 of X is between about 3.7A" and about 52A", and 16 when the width of X is greater than about 5.2A, from a mixture containing the same and an aliphatic compound represented by general formula (E) than X. and r and m are integers the sum of which is other than n-2, which comprises: con- :tactingrgsaid mixture, appropriate orf :the ormation of a: crystalline urea-amstel" .cnndtions complex of urea: andisaidtcomponnd iti-)gnand separating saidcomplex from the resulting reaction mixture. K

8. Crystalline complex of urea and a straight than Vabout V512A".

1.-i9.=C'r-yetalline complex 'of ureaand a saturated 'fstnaight chain aliphatie VcompoundY containing `a sulfur-containing terminal substituentandhaving in the chain atleast about: 12 to V18 carbon atoms When `the Widt of said substituent is j'between about S'A" and'V about 51.2A,- and 18 jaibon atoms when the Width ofllsaid- 'sbstituent is greater than about`512li".

' 410. 'Crystalline complex ourea'and afsaturated "straight chain paraffin-having one sulfate-terminal substituent 'and hatingv Vat lleast about 12 carbon atoms VVin I"the chain.

11. Crystalline oomplexiof urea and a straight chain aliphatic compound containing a sulfurcontaining substituent joined to other than a V'jterinn'inal carbon atornand4 having 'in the chain at fleastfabout: 1..-8 "f to -Zfearbon atoms: whennth'e length of .saidsubstituent :betweenzifabout -.2;8A;and1 about 91.2.5111 and 24 carbon atomstwhen the length of said substituent visgreater than. about 32A"-` lf2. The method of. separating amstraightchain aliphatic-compound y(I) containing` asultur-containing `substituent rjoined. to other than :aterminal carbon atom :thereof and having,r inthe chain atleast about: 18 to 24' carbon atomsvwhen the .lengthmofsaid substituentis between about 2.8A-and about 3,2fansi.` 2e' carbon-.atoms .when the length of .said substituent `ris greater than about 3.2M', froma mixture-containing` thefsame and atzleast one sulfur-containing compoundsztf) less susceptible to-urea .complex `formation than saiclsulfur-eontaining compound which-oom :prises: contacting4 said mixture with ureaunder oondjtionsuappropriate -for the vformation tof :a crystalline complex of. urea .and said sulfur-con `taining compound (I): and separating lsaidfcomplex from'thefresultlng reaction mixture.V`

Qaeferences Vcited in .the meer thisfpatnt UNrrED STATES PATENTS Name Date Fetterly 'Aug.l29`, 1950 Number. 

1. THE METHOD OF SEPARATING A STRAIGHT CHAIN ALIPHATIC COMPOUND (I) CONTAINING A SULFUR-CONTAINING TERMINAL SUBSTITUTENT AND HAVING IN THE CHAIN AT LEAST ABOUT: 12 TO 18 CARBON ATOMS WHTN THE "WIDTH" OF SAID SUBSTITUENT IS BETWEEN ABOUT 3.7A* AND ABOUT 5.2A* AND 18 CARBON ATOMS WHEN THE "WIDTH" OF SAID SUBSTITUENT IS GREATER THAN ABOUT 5.2A*, FROM A MIXTURE CONTAINING THE SAME AND AT LEAST ONE SULFUR-CONTAINING COMPOUND (II) LESS SUSCEPTIBLE TO UREA COMPLEX FORMATION THAN SAID SULFUR-CONTAINING COMPOUND (I) WHICH COMPRISES: CONTACTING SAID MIXTURE WITH UREA UNDER CONDITIONS APPROPRIATE FOR THE FORMATION OF A CRYSTALLINE COMPLEX OF UREA AND 